bearfrieze

Comprehensions in Python the Jedi way

by Bjørn Friese

Beautiful is better than ugly. Explicit is better than implicit.

-- The Zen of Python

I frequently deal with collections of things in the programs I write. Collections of droids, jedis, planets, lightsabers, starfighters, etc. When programming in Python, these collections of things are usually represented as lists, sets and dictionaries. Oftentimes, what I want to do with collections is to transform them in various ways. Comprehensions is a powerful syntax for doing just that. I use them extensively, and it's one of the things that keep me coming back to Python. Let me show you a few examples of the incredible usefulness of comprehensions.

pudquick

import os.path
from Foundation import NSData, NSKeyedUnarchiver, SFLListItem, NSURL, NSMutableDictionary, NSKeyedArchiver, NSString, NSDictionary, NSArray

def load_favservers(sfl_path):
    if os.path.isfile(sfl_path):
        # File exists, use it
        sfl_decoded = NSKeyedUnarchiver.unarchiveObjectWithData_(NSData.dataWithContentsOfFile_(sfl_path))
    else:
        # File doesn't exist, make a blank template
        sfl_decoded = {u'items': [],

arubdesu

#!/usr/bin/python
"""Enables location services, allows Maps and Timezone"""
import os
import platform
import subprocess
import sys
try:
    sys.path.append('/usr/local/munki/munkilib/')
    import FoundationPlist
except ImportError as error:

pudquick

from ctypes import CDLL

loginPF = CDLL('/System/Library/PrivateFrameworks/login.framework/Versions/Current/login')
result = loginPF.SACLockScreenImmediate()

grahamgilbert

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>PayloadContent</key>
    <array>
      <dict>
          <key>PayloadType</key>
          <string>com.apple.applicationaccess.new</string>
          <key>PayloadVersion</key>

apettinen

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>PayloadIdentifier</key>
    <string>YOUR IDENTIFIER HERE</string>
    <key>PayloadRemovalDisallowed</key>
    <false/>
    <key>PayloadScope</key>
    <string>System</string>

pudquick

from Foundation import NSKeyedUnarchiver
from struct import unpack

# This entire function is black magic of the highest order and I'll blog about it later
def extract_share(bookmark_data):
    content_offset, = unpack('I', bookmark_data[12:16])
    first_TOC, = unpack('I', bookmark_data[content_offset:content_offset+4])
    first_TOC += content_offset
    TOC_len, rec_type, level, next_TOC, record_count = unpack('IIIII', bookmark_data[first_TOC:first_TOC+20])
    TOC_cursor = first_TOC + 20

cabeca

#!/usr/bin/env ruby

require 'JSON'

device_types = JSON.parse `xcrun simctl list -j devicetypes`
runtimes = JSON.parse `xcrun simctl list -j runtimes`
devices = JSON.parse `xcrun simctl list -j devices`

devices['devices'].each do |runtime, runtime_devices|
  runtime_devices.each do |device|

bruienne

onLogout() {
    # Insert whatever script you need to run at logout
    exit
}

echo "INFO - Watching ${HOME}" >> /var/log/org.my.log

trap 'onLogout' SIGINT SIGHUP SIGTERM

while true; do

bruienne

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Label</key>
	<string>org.my.logoutwatcher</string>
	<key>ProgramArguments</key>
	<array>
		<string>/usr/local/myorg/logoutwatcher.sh</string>
	</array>